In a number of applications, it can be desirable to measure the width of a pulse in an electrical signal. For example, measurement of the pulse width of a train of pulses output from a tyre-mounted monitoring device can be used in the estimation of the size of the footprint of the tyre, which in turn can be used to estimate other characteristics of the tyre.
This may be achieved in the time domain by low-pass filtering the pulse signal in order to reduce noise, then measuring the time between two carefully selected reference points in the signal (e.g. the crossing of a specific threshold level). Unfortunately, in a poor signal-to-noise ratio condition, relatively heavy filtering is required to reduce the noise and this can affect the shape of the signal, thus changing its width. Also, depending on the shape of the pulse, the selection of the reference points can be difficult and not sufficiently general to suit every possible situation. The design of a suitable filter depends on width and rate of the pulses; if these change, then the filter should be adjusted accordingly and in real time in order to maintain the best noise reduction and limiting the pulse distortion. Finally, sharp filters introduce ripple in the signal which may trigger false detections.
It would be desirable to provide an improved pulse width measurement method and apparatus.